The present invention relates generally to the telephone art, and more particularly concerns improvements in automatic number identification (ANI) systems.
In those telephone systems using central automatic switching facilities (central offices), it is often desirable that the number of the party placing a long-distance (toll) call be automatically identified, for purposes of accurate, economical billing. This is currently done for those parties which have a single party line, i.e., only one party on a single communication line pair connection to the central office, by well-known equipment which identifies the particular line pair over which the call occurs and from that identifies the calling party. However, a serious problem in the automatic identification of the calling party is presented when two parties are connected to the same communication line pair, a condition known in the telephone art as a two-party line. One conventional system used to automatically distinguish between two parties common to a single communication line pair is known in the art as resistance ground automatic number identification. In such a system, one of the parties to the two-party line has an identification circuit, which includes an element referred to in the art as a ground mark circuit, present in his telephone instrument. The other party to the two-party line either does not have such an identification circuit in his telephone instrument or, if it is present, it is disabled. The two parties thus may be distinguished from each other at the central office on the basis that one party has an enabled identification circuit in his telephone, and the other does not. The actual operation of the identification circuit will be discussed in more detail in later paragraphs.
Typically, an identification circuit is physically incorporated in each telephone manufactured, but it is not until the telephone is actually installed that the identification circuit contained therein is made operable, or alternatively, is disabled. The operational condition of the identification circuit of a given telephone will of course, be opposite to the operating condition of the identification circuit present in the telephone of the other party (if any) on the two-party line.
It is sometimes inconvenient for a telephone company, however, to enable or disable the identification circuit at the time of installation of the telephone. Additionally, when a group of existing telephones are being converted from operator number identification (ONI) to automatic number identification (ANI), burdensome problems of arranging for home visits to install identification circuits are presented. Furthermore, with the decline of telephone leasing, and with a corresponding increase in the number of telephones which are purchased and installed by subscribers, the control of a telephone company over the individual telephones in its system has significantly decreased. Not surprisingly, these problems of installation and control have caused numerous errors in proper identification of and billing of parties placing long-distance calls.
Accordingly, it is a general object of the present invention to provide an ANI identification circuit which overcomes the disadvantages of the prior art described above.
It is a further object of the present invention to provide such an identification circuit which is compatible with existing ANI equipment, and which may be installed on a subscriber's line without access to the subscriber's telephone.
It is yet another object of the present invention to provide such an identification circuit which is activated only upon lifting of the receiver of one telephone on the two-party line.
It is another object of the present invention to provide such an identification circuit which may be installed at any place on the line between a subscriber's telephone and the point of intersection with the line of the other party on the two-party line.